Certain embodiments of the present invention generally relate to a coaxial cable displacement contact having a displacement beam configuration that facilitates manual and automated assembly of a connector and a coaxial cable. Other embodiments of the present invention generally relate to methods of manufacture for coaxial cable displacement contacts and their assembly with a coaxial cable.
In the past, connectors have been proposed for interconnecting coaxial cables. Generally, coaxial cables have a circular geometry formed with a central conductor (of one or more conductive wires) surrounded by a cable dielectric material. The dielectric material is surrounded by a cable braid (of one or more conductive wires), and the cable braid is surrounded by a cable jacket. In most coaxial cable applications, it is preferable to match the impedance between source and destination electrical components located at opposite ends of the coaxial cable. Consequently, when sections of coaxial cable are interconnected, it is preferable that the impedance remain matched through the interconnection.
Conventional coaxial connectors are formed from generally circular components partly to conform to the circular geometry of the coaxial cable. Circular components are typically manufactured using screw machining and diecast processes that may be difficult to implement. As the difficulty of the manufacturing process increases, the cost to manufacture each individual component similarly increases. Accordingly, conventional coaxial connectors have proven to be somewhat expensive to manufacture. Many of the circular geometries for coaxial connectors were developed based on interface standards derived from military requirements. These more costly manufacturing processes for the circular geometries were satisfactory for low volume, high priced applications, as in military systems and the like.
Today, however, coaxial cables are becoming more widely used. The wider applicability of coaxial cables demands a high-volume, low-cost manufacturing process for coaxial cable connectors. Recently, demand has arisen for radio frequency (RF) coaxial cables in applications such as the automotive industry. The demand for RF coaxial cables in the automotive industry is due in part to the increased electrical content within automobiles, such as AM/FM radios, cellular phones, GPS, satellite radios, Blue Tooth(trademark) compatibility systems and the like. Also, conventional techniques for assembling coaxial cables and connectors are not suitable for automation, and thus are time consuming and expensive. Conventional assembly techniques involve the following general procedure:
a) after sliding a ferrule over the cable, stripping the jacket to expose the outer conductive braid,
b) folding the outer conductive braid back over the ferrule to expose a portion of the dielectric layer,
c) stripping the exposed portion of the dielectric layer to expose a portion of the inner conductor,
d) connecting a contact to the inner conductor, and
e) connecting a contact to the outer conductive braid.
The above-noted procedure for assembling a connector and a coaxial cable is not easily automated and requires several manual steps that render the procedure time consuming and expensive.
Today""s increased demand for coaxial cables has caused a need to improve the design for coaxial connectors and the methods of manufacture and assembly thereof.
In accordance with one aspect of the present invention, a connector is provided with a coaxial cable displacement contact connectable to at least one outer conductor, for example a conductive braid. The coaxial cable displacement contact includes a displacement beam insertable into the coaxial cable. The displacement beam and an associated wall define a braid-receiving slot spaced to receive the outer conductive braid of the coaxial cable when the displacement beam is inserted into the coaxial cable. Optionally, the connector may include a pair of coaxial cable displacement contacts with respective displacement beams spaced apart by a distance greater than a diameter of the inner conductor of the coaxial cable such that both of the displacement beams pierce the outer conductive braid of the coaxial cable.
In accordance with another aspect of the present invention, a method is provided for mounting a connector to a coaxial cable having inner and outer conductors separated by a dielectric layer. The method includes exposing an end portion of an inner conductor of the coaxial cable and securing an inner contact to the end portion of the inner conductor. The coaxial cable and inner contact are positioned in an insulated housing with the inner and outer conductors of the coaxial cable extending along a longitudinal axis of the insulated housing. An outer contact is laterally inserted onto the coaxial cable in a direction transverse to the longitudinal axis until the outer contact pierces the coaxial cable, exerts a retention force on the outer conductor, and makes electrical connection therewith.
Optionally, each of a pair of outer contacts may laterally pierce an associated coaxial cable. When inserting the outer contacts, each coaxial cable is centered over a gap between a pair of displacement beams provided in an associated outer contact. The method then includes piercing the coaxial cable with the displacement beams until the displacement beams electrically engage and exert a retention force upon the outer conductor (e.g., a friction force of desired magnitude sufficient to hold the outer contact on the coaxial cable under certain conditions). Optionally, the method includes laterally inserting an inner contact into a slot in a side of the insulated housing along a direction transverse to the longitudinal axis of the insulated housing. Optionally, the method includes orienting the inner and outer contacts in parallel planes extending parallel to the longitudinal axis.
In accordance with another aspect of the present invention, a coaxial cable displacement contact is provided for connection with a coaxial cable having an inner conductor and an outer conductor separated by a dielectric layer and encased in a jacket. The coaxial cable displacement contact comprises a forked section having a displacement beam and contact wall separated by a braid-receiving slot. The braid-receiving slot has a slot width corresponding to a radial width of an outer conductor of a coaxial cable. The displacement beam is positioned to displace a portion of a dielectric layer and a jacket during insertion. The displacement beam is configured to induce lateral retention forces on a section of an outer conductor of a coaxial cable wedged in the braid-receiving slot.
Optionally, two coaxial cable displacement contacts comprising two respective displacement beams may be provided which are separated by a cable channel configured to receive an inner conductor and a portion of a dielectric layer surrounding an inner conductor of a coaxial cable. The cable channel has a width less than an inner diameter of an outer conductor of the coaxial cable.
In accordance with another aspect of the present invention, a strain relief is provided for a coaxial cable connector. The strain relief includes a strain relief crimp and a strain relief member. The strain relief crimp includes a body portion with arms secured to opposite ends thereof and with a cable grip formed in the center of the body portion. The cable grip is configured to pierce a jacket of a coaxial cable and engage an outer conductor thereof. The arms include ribs along opposite sides thereof. The strain relief member includes a base configured to receive a coaxial cable and having channels extending through the base along opposite ends thereof. The channels are dimensioned and aligned to frictionally receive and retain the arms. The cable grip pierces the jacket of the coaxial cable and engages the outer conductor to resist movement between the coaxial cable and the strain relief crimp when the strain relief crimp and strain relief member are joined. The cable grip affords secure engagement between the strain relief and the coaxial cable without the need for the strain relief to apply lateral forces to the coaxial cables so strong as to deform the circular geometry of the coaxial cable which may otherwise impair the signal performance and impedance thereof.
Optionally, the coaxial cable displacement contact may further include a cable retention housing having a channel with a radiused inner surface conforming to a shape of, and configured to receive, a coaxial cable. The cable retention housing has a guideway for slidably receiving the coaxial cable displacement contact in an orientation transverse to an axis of the channel. The housing includes a channel with an inner contour conforming to a shape of a coaxial cable to prevent deformation of the coaxial cable when the displacement beam pierces the jacket and outer conductor of a coaxial cable. Optionally, the coaxial cable displacement contact may be provided with a cable support configured to orient a coaxial cable along a predefined cable axis. The cable support includes opposed contact guides oriented in a plane transverse to the predefined cable axis. The contact guides slidably receive and align opposite ends of the coaxial cable displacement contact to guide the displacement beam onto the outer conductor of a coaxial cable.